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CN109712398B - Expressway travel time estimation model parameter optimization method - Google Patents

Expressway travel time estimation model parameter optimization method Download PDF

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CN109712398B
CN109712398B CN201910060915.4A CN201910060915A CN109712398B CN 109712398 B CN109712398 B CN 109712398B CN 201910060915 A CN201910060915 A CN 201910060915A CN 109712398 B CN109712398 B CN 109712398B
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travel time
time estimation
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road section
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CN109712398A (en
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吕伟韬
杨树
陈凝
饶欢
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Jiangsu Zhitong Traffic Technology Co ltd
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    • GPHYSICS
    • G08SIGNALLING
    • G08GTRAFFIC CONTROL SYSTEMS
    • G08G1/00Traffic control systems for road vehicles
    • G08G1/01Detecting movement of traffic to be counted or controlled
    • G08G1/052Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
    • GPHYSICS
    • G08SIGNALLING
    • G08GTRAFFIC CONTROL SYSTEMS
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Abstract

The invention provides a parameter optimization method of a highway travel time estimation model, which comprises the steps of constructing a route travel time estimation model comprising a plurality of road sections based on a road section travel time estimation model; optimizing model parameters l, m and alpha by adopting a genetic algorithm; defining a genetic algorithm fitness function
Figure DDA0001953292590000011
Wherein Wj is an error index MAjJ is the time interval of the travel time estimation, and the value range is [2, K ]]The optimization goal of the genetic algorithm is that the fitness function is minimum; calculating the weight Wj by using an M-H algorithm; outputting the optimal parameter combination [ l, m, alpha ] under the free flow state and the congestion state by a genetic algorithm](ii) a Further establishing an optimized route travel time estimation model; according to the method, the sensitivity of the model to different traffic running states such as congestion and smoothness is improved by automatically optimizing the parameters of the travel time estimation model, the travel time estimation precision under the congestion condition is obviously improved, and the reliability and stability of the model performance are guaranteed.

Description

Expressway travel time estimation model parameter optimization method
Technical Field
The invention relates to a method for optimizing parameters of an expressway travel time estimation model.
Background
The travel time is one of important indexes for evaluating traffic operation congestion conditions, and the travel time can provide data reference for implementation of a traffic guidance scheme and release of travel information during traffic guidance, and is the most intuitive basis for travelers to make travel decisions.
The current travel time parameters are acquired indirectly through a certain data processing means based on traffic flow parameters acquired by fixed detection equipment. The expressway travel time estimation model can be divided into a track-based estimation model, a vehicle identification model and a traffic flow theoretical model.
However, many current travel time estimation models have the problem of model performance stability, and particularly under congested road conditions, the accuracy of travel time estimation is low. The above-mentioned problem is a problem that should be considered and solved in the highway travel time estimation process.
Disclosure of Invention
The invention aims to provide a method for optimizing parameters of a highway travel time estimation model, which ensures that the model has good estimation precision in different running states, and solves the problems that the current travel time estimation model in the prior art has model performance stability, and particularly the travel time estimation precision is low under congested road conditions.
The technical solution of the invention is as follows:
a method for optimizing the parameters of the travel time estimation model of expressway includes such steps as,
s1, respectively setting virtual following vehicles VF and front vehicles VL at node positions Su and Sd of upstream and downstream detectors of a road section, constructing a GM following model, describing the operation parameter relationship between the front vehicles and the following vehicles, and constructing a road section travel time estimation model GMTTE on the basis:
Figure GDA0002979155910000011
the model outputs a virtual following vehicle VF on a road section IthUpper travel time TTIAnd on the road section IthDownstream endpoint real time velocity
Figure GDA0002979155910000012
Wherein v isSd、vSuAs input values for the model, respectively for the section IthA speed detection value output by the upstream and downstream detectors; l is the locomotive spacing index, m is the speed index, and alpha is the sensitivity; further constructing a route travel time estimation model comprising a plurality of road segments based on the road segment travel time estimation model;
the values of the S2, l, m and alpha parameters directly influence the travel time estimation precision, and a genetic algorithm fitness function is predefined
Figure GDA0002979155910000021
Wherein Wj is an error index MAjJ is the time interval of the travel time estimation, and the value range is [2, K ]]The optimization target of the genetic algorithm is the minimum fitness function;
s3, initializing the weight of the genetic algorithm fitness function, namely p (j) ═ Wj, and determining p (j) prior distribution according to the traffic flow state; calculating error index MAj(l, m, alpha), updating the weight by adopting a Metropolis-Hastings algorithm, iteratively calculating the optimal solution of the time interval j of travel time estimation through a genetic algorithm, and determining the corresponding weight Wj;
s4, based on the optimal solution corresponding weight determined by S3, outputting an optimal parameter combination [ l, m, alpha ] in a free flow state and a congestion state by a genetic algorithm, and optimizing the initial route travel time estimation model constructed by S1.
Further, in step S1, a route travel time estimation model including a plurality of road segments is constructed, specifically:
s11, using the distribution point of the highway traffic flow detector as the road segment dividing node in the route, numbering the road segments (I + k)thI is a route number, k is a road section serial number, th is a road section number mark, and k belongs to [0, n ]]I.e. the route is divided into n +1 road segments;
s12, for any road section (I + k)thVirtual following vehicles VF and virtual leading vehicles VL are respectively arranged at the upstream detector node position Su and the downstream detector node position Sd; the real-time running speed of VL is calculated according to a speed detection value output by a downstream detector node position Sd detector, and the formula is as follows:
Figure GDA0002979155910000022
where T ∈ [ T ]i,Ti+1],TiA data timestamp for the downstream detector node location Sd detector,
Figure GDA0002979155910000023
respectively at time stamp T for the detectori、Ti+1A running speed detection value of (1);
s13, constructing a road section travel time estimation model GMTTE according to the relation between the GM following model and the operation parameters of the leading vehicle and the following vehicle:
Figure GDA0002979155910000024
the model outputs a virtual following vehicle VF on a road section IthUpper travel time TTIAnd on the road section IthDownstream endpoint real time velocity
Figure GDA0002979155910000025
Wherein v isSd、vSuAs input values for the model, respectively for the section IthThe speed detection values output by the upstream detector and the downstream detector; l is the locomotive spacing index, m is the speed index, and alpha is the sensitivity; on this basis, the route travel time is estimated.
Further, in step S13, the route travel time is estimated, specifically,
s131, following vehicle VF on road section IthReal-time running speed at any time t of up running
Figure GDA0002979155910000031
The calculation formula is as follows:
Figure GDA0002979155910000032
in the formula
Figure GDA0002979155910000033
The running speed and the acceleration of VF at the time of T-delta T and the real-time acceleration
Figure GDA00029791559100000318
The specific calculation formula is as follows:
Figure GDA0002979155910000034
in the formula
Figure GDA0002979155910000035
The running speed of the lead vehicle at the moment T-delta T,
Figure GDA0002979155910000036
respectively the running distance of the leading vehicle and the following vehicle at the time of T-delta T and the real-time running distance of the VL of the leading vehicle
Figure GDA0002979155910000037
The calculation formula is as follows:
Figure GDA0002979155910000038
real-time driving distance of following vehicle VF
Figure GDA0002979155910000039
The calculation formula is as follows:
Figure GDA00029791559100000310
in the formula
Figure GDA00029791559100000311
The running speed of the lead vehicle at the moment T-delta T,
Figure GDA00029791559100000312
for the running distance of the following vehicle at the time T-delta T,
Figure GDA00029791559100000313
the acceleration of VF at the time T-delta T;
s132, taking the road section IthEnd point real time velocity vTTIFor following car VF on the next road section (I +1)thInitializing the speed of the starting point;
s133, estimating model by using road section travel time
Figure GDA00029791559100000314
Estimation section (I +1)thThe travel time of (a);
s134, circulating the steps S132 and S133 until the road section (I + n) is finishedthA travel time estimate of (d);
s135, route travel time
Figure GDA00029791559100000315
Wherein TTIFor following vehicle VF on road section IthUpper travel time.
Further, in step S3, specifically,
s31, initializing weights, i.e., p (j) ═ Wj; the prior distribution p (j) is selected according to the traffic flow running state, and the traffic flow running state comprises a free flow state and a congestion state;
s32, calculating an error index MAj(l, m, α), adding MAjThe minimum value of the corresponding j is taken as the optimal time interval; the genetic algorithm outputs an optimal solution every iteration
Figure GDA00029791559100000316
Wherein M is the number of iterations;
s33, passing the optimal solution
Figure GDA00029791559100000317
And updating the prior distribution in the two operation states in the step S31 to generate the posterior distribution of the optimal solution.
Further, in step S31, the prior distribution p (j) is selected according to the traffic flow running state, specifically,
using uniform probability distribution in free-flow regime, i.e.
Figure GDA0002979155910000041
σ1、σ2The upper and lower limits of j are defined according to the definition of the value range in S2, σ1=2,σ2=K;
Using lognormal distribution in congested conditions, i.e.
Figure GDA0002979155910000042
μ and σ are the mean and standard deviation of j, respectively.
Further, in step S33, specifically,
s331, representing the known optimal solution j by Gaussian distributionoldAnd iterating the newly generated optimal solution jnewThe probability relationship between p (j)new|jold)=N(joldr) Wherein j isoldThe initial value is set to a non-negative number, σrIs the step length;
s332, calculating likelihood ratio r, and judging jnewWhether it is acceptable; in the free flow state, the calculation formula of r is as follows:
Figure GDA0002979155910000043
in the congestion state, the calculation formula of r is as follows:
Figure GDA0002979155910000044
if r > 1, then jnewAcceptable, the current optimal solution is calculated by joldIs updated to jnewOtherwise, it remains as jold
S333, performing N-fold loop on the steps S331 and S332 to obtain the optimal solution J of the time interval J and the corresponding weight WJ
The invention has the beneficial effects that:
according to the method for optimizing the parameters of the expressway travel time estimation model, the sensitivity of the model to different traffic running states such as congestion and unblocked traffic is improved by automatically optimizing the parameters of the travel time estimation model, the travel time estimation precision under the congestion condition is obviously improved, and the reliability and stability of the model performance are guaranteed.
The method for optimizing the parameters of the expressway travel time estimation model estimates the travel time of the road section based on the GM following model, and then establishes a route travel time estimation model by applying a continuous speed model on the basis of the estimation of the travel time of the expressway, so that the estimation of the travel time of the route is realized.
The method for optimizing the parameters of the expressway travel time estimation model fully utilizes distributed computing performance, optimizes the parameters of the route travel time estimation model by adopting a parallel genetic algorithm and a Metropolis-Hastings algorithm, fully considers the influence of different congestion levels on the travel time estimation model, and further improves the accuracy of the model in forming estimation on the congested and unblocked routes in different running states.
Drawings
FIG. 1 is a flow chart of a method for optimizing parameters of a highway travel time estimation model according to an embodiment of the invention.
Fig. 2 is a schematic diagram of setting the virtual leading vehicle VL and the following vehicle VF in the embodiment.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Examples
According to the method for optimizing the parameters of the expressway travel time estimation model, a road section GMTTE (General Motor's travel time estimation) travel time estimation model is combined with a continuous speed model, the estimation of the route travel time is realized, the distributed computing performance is fully utilized, the parameters of the route travel time estimation model are optimized by adopting a parallel genetic algorithm, the influence of different congestion levels on the travel time estimation model is fully considered, and the accuracy of the model in estimation of congested and unblocked routes in different running states is further improved.
A method for optimizing parameters of an expressway travel time estimation model, as shown in figure 1, comprises the following steps,
s1, respectively setting virtual following vehicles VF and front vehicles VL at node positions Su and Sd of upstream and downstream detectors of a road section, constructing a GM following model, describing the operation parameter relationship between the front vehicles and the following vehicles, and constructing a road section travel time estimation model GMTTE on the basis:
Figure GDA0002979155910000051
the model outputs a virtual following vehicle VF on a road section IthUpper travel time TTIAnd on the road section IthDownstream endpoint real time velocity
Figure GDA0002979155910000052
Wherein v isSd、vSuAs input values for the model, respectively for the section IthA speed detection value output by the upstream and downstream detectors; l is the locomotive spacing index, m is the speed index, and alpha is the sensitivity; further constructing a route travel time estimation model comprising a plurality of road segments based on the road segment travel time estimation model; the method comprises the following specific steps:
s11, using the distribution point of the highway traffic flow detector as the road segment dividing node, and numbering the road segments (I + k)thI is a route number, k is a road section serial number, th is a road section number mark, and k belongs to [0, n ]]I.e. the route is divided into n +1 road segments.
S12, for any road section (I + k)thVirtual following vehicles VF and virtual leading vehicles VL are respectively arranged at the upstream detector node position Su and the downstream detector node position Sd, as shown in fig. 2; the real-time running speed of VL is calculated according to a speed detection value output by a node position Sd detector of a downstream detector, and the formula is as follows:
Figure GDA0002979155910000061
where T ∈ [ T ]i,Ti+1],TiIs the data time stamp of the Sd detector,
Figure GDA0002979155910000062
Figure GDA0002979155910000063
respectively at time stamp T for the detectori、Ti+1The detected average traveling speed.
S13, according to the definition of the GM car following model on the operation parameter relation between the leading car and the car following, constructing a road section travel time estimation model GMTTE:
Figure GDA0002979155910000064
the model outputs a virtual following vehicle VF on a road section IthUpper travel time TTIAnd on the road section IthDownstream endpoint real time velocity vTTIWherein v isSd、vSuAs input values for the model, respectively for the section IthThe speed detection values output by the upstream detector and the downstream detector; l is the locomotive spacing index, m is the speed index, and alpha is the sensitivity; the process is repeated until the road segment (I + n) is completedthEstimating the travel time of the route, and further estimating the travel time of the route; in particular, the amount of the solvent to be used,
s131, following vehicle VF on road section IthReal-time running speed at any time t of up runningDegree of rotation
Figure GDA0002979155910000065
The calculation formula is as follows:
Figure GDA0002979155910000066
in the formula
Figure GDA0002979155910000067
The running speed and the acceleration of VF at the time of T-delta T and the real-time acceleration
Figure GDA0002979155910000068
The specific calculation formula is as follows:
Figure GDA0002979155910000069
wherein a (—) is the sensitivity,
Figure GDA00029791559100000610
the running speed of the lead vehicle at the moment T-delta T,
Figure GDA00029791559100000611
respectively the running distance of the leading vehicle and the following vehicle at the time of T-delta T and the real-time running distance of the VL of the leading vehicle
Figure GDA00029791559100000612
The calculation formula is as follows:
Figure GDA00029791559100000613
real-time driving distance of following vehicle VF
Figure GDA00029791559100000614
The calculation formula is as follows:
Figure GDA00029791559100000615
in the formula
Figure GDA00029791559100000616
The running speed of the lead vehicle at the moment T-delta T,
Figure GDA00029791559100000617
for the running distance of the following vehicle at the time T-delta T,
Figure GDA00029791559100000618
the acceleration of VF at time T- Δ T.
S132, taking the road section IthEnd point real time velocity vTTIFor following car VF on the next road section (I +1)thThe speed of the starting point is initialized.
S133, estimating model by using road section travel time
Figure GDA0002979155910000071
Estimation section (I +1)thThe travel time of (c).
S134, circulating the steps S132 and S133 until the road section (I + n) is finishedthIs estimated.
S135, route travel time
Figure GDA0002979155910000072
Wherein TTIFor following vehicle VF on road section IthUpper travel time.
The values of the S2, l, m and alpha parameters directly influence the travel time estimation precision, and a genetic algorithm fitness function is predefined
Figure GDA0002979155910000073
Wherein Wj is an error index MAjJ is the time interval of the travel time estimation, and the value range is [2, K ]]The time unit is minute (min), in the embodiment, the maximum estimation interval K of the travel time is 15, that is, the upper and lower limits of the estimation interval of the travel time are 2min and 15min respectively; wherein, the error index MA is selected from the average absolute error MAE and the average absolute percentage error MAPE; the genetic algorithm optimization goal is that the fitness function is minimal.
S3, initializing the weight of the genetic algorithm fitness function, namely p (j) ═ Wj, and determining p (j) prior distribution according to the traffic flow state; calculating error index MAj(l, m, α) using Metropolis-HastingsUpdating the weight by the method, iteratively calculating the optimal solution of the time interval j of the travel time estimation through a genetic algorithm, and determining the corresponding weight Wj; the specific calculation method comprises the following steps:
s31, initializing weights, i.e., p (j) ═ Wj; wherein the prior distribution p (j) is selected according to the traffic flow running state and adopts uniform probability distribution in the free flow state, i.e.
Figure GDA0002979155910000074
σ1、σ2Respectively, the upper and lower value limits of j, according to the definition of the value range of the j in the step S2, sigma1=2,σ215; using lognormal distribution in congested conditions, i.e.
Figure GDA0002979155910000075
Wherein μ and σ are the mean value and standard deviation of j, μ is 3, and σ is 1, respectively.
S32, calculating an error index MAj(l, m, α), adding MAjThe minimum value of the corresponding j is taken as the optimal time interval; the genetic algorithm outputs an optimal solution every iteration
Figure GDA0002979155910000076
Where M is the number of iterations.
S33, passing the optimal solution
Figure GDA0002979155910000077
Updating prior distributions in the two running states of S31 to generate posterior distribution of an optimal solution; the method comprises the following specific steps:
s331, representing the known optimal solution j by Gaussian distributionoldAnd iterating the newly generated optimal solution jnewThe probability relationship between p (j)new|jold)=N(joldr) Wherein j isoldThe initial value is set to a non-negative number, in the embodiment 10, step size σrThe value is 5;
s332, calculating likelihood ratio r, and judging jnewWhether it is acceptable; in the free flow state, the calculation formula of r is as follows:
Figure GDA0002979155910000081
in the congestion state, the calculation formula of r is as follows:
Figure GDA0002979155910000082
if r > 1, then jnewAcceptable, the current optimal solution is calculated by joldIs updated to jnewOtherwise, it remains as jold
S333, performing N-fold circulation on S331 and S332 to obtain an optimal solution J of a time interval J and a corresponding weight Wi(ii) a Wherein, in the embodiment, the value of N is 2000.
S4, outputting an optimal parameter combination [ l, m, alpha ] in a free flow state and a congestion state by a genetic algorithm based on the optimal solution corresponding weight determined in the step S3; the initial route travel time estimation model constructed in step S1 is optimized.
According to the method for optimizing the parameters of the expressway travel time estimation model, the parameters of the travel time estimation model are automatically optimized, so that the sensitivity of the model to different traffic running states such as congestion and unblocked traffic is improved, the travel time estimation precision under the congestion condition is obviously improved, and the reliability and stability of the model performance are guaranteed.
The method for optimizing the parameters of the expressway travel time estimation model estimates the travel time of the road section based on the GM following model, and on the basis, a continuous speed model is applied to construct a route travel time estimation model to realize the estimation of the route travel time. According to the method for optimizing the parameters of the expressway travel time estimation model, the parameters of the route travel time estimation model are automatically optimized by adopting a genetic algorithm and a Metropolis-Hastings algorithm, and the reliability of travel time estimation performance in different running states of traffic flow is improved.
One specific example of an embodiment is as follows:
the method comprises the steps of adopting an optimization model optimized and constructed by the method of the embodiment to estimate the travel time of two expressway routes, wherein the total length of the route is 11.59km, the number of lanes is 3, the selected analysis time period is 7: 00-8: 00, the traffic flow is mostly in a smooth state in the time period, the total length of the route is 5.95km, the number of lanes is 4, the analysis time period is 7: 50-8: 50, and congestion occurs frequently in the time period. 183 pieces and 285 pieces of real data of the travel time of the two lines are obtained respectively to calculate estimation errors.
In the embodiment, when the genetic algorithm definition is performed in step S2, the mean absolute error MAE and the mean absolute percentage error MAPE are respectively used as error indicators to establish a fitness function, so as to perform parameter optimization, and the final model parameter optimization result is as shown in the following table.
Taking the MAPE as an error index, the road section travel time estimation model GMTTE of the route 1 is as follows:
Figure GDA0002979155910000091
section travel time estimation model GMTTE of route 2:
Figure GDA0002979155910000092
according to
Figure GDA0002979155910000093
Estimating the route travel time; with MAE as an error index, a road section travel time estimation model GMTTE of the route 1 is as follows:
Figure GDA0002979155910000094
section travel time estimation model GMTTE of route 2:
Figure GDA0002979155910000095
according to
Figure GDA0002979155910000096
A route travel time estimate is made.
Figure GDA0002979155910000097

Claims (6)

1. A method for optimizing parameters of an expressway travel time estimation model is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
s1, upper and lower road sectionsVirtual following vehicles VF and virtual leading vehicles VL are respectively arranged at the node positions Su and Sd of the trip detectors, a GM following model is constructed, the operation parameter relation between the leading vehicles and the following vehicles is described, and a section travel time estimation model GMTTE is constructed on the basis:
Figure FDA0002979155900000011
the model outputs a virtual following vehicle VF on a road section IthUpper travel time TTIAnd on the road section IthDownstream endpoint real time velocity
Figure FDA0002979155900000012
Wherein v isSd、vSuAs input values for the model, respectively for the section IthA speed detection value output by the upstream and downstream detectors; l is the locomotive spacing index, m is the speed index, and alpha is the sensitivity; further constructing a route travel time estimation model comprising a plurality of road segments based on the road segment travel time estimation model;
the values of the S2, l, m and alpha parameters directly influence the travel time estimation precision, and a genetic algorithm fitness function is predefined
Figure FDA0002979155900000013
Wherein Wj is an error index MAjJ is the time interval of the travel time estimation, and the value range is [2, K ]]The optimization target of the genetic algorithm is the minimum fitness function;
s3, initializing the weight of the genetic algorithm fitness function, namely p (j) ═ Wj, and determining p (j) prior distribution according to the traffic flow state; calculating error index MAj(l, m, alpha), updating the weight by adopting a Metropolis-Hastings algorithm, iteratively calculating the optimal solution of the time interval j of travel time estimation through a genetic algorithm, and determining the corresponding weight Wj;
s4, based on the optimal solution corresponding weight determined in the step S3, outputting an optimal parameter combination [ l, m, alpha ] in a free flow state and a congestion state by a genetic algorithm, and optimizing the initial route travel time estimation model constructed in the step S1.
2. The method of optimizing highway travel time estimation model parameters according to claim 1, wherein: in step S1, a route travel time estimation model including a plurality of road segments is constructed, specifically:
s11, using the distribution point of the highway traffic flow detector as the road segment dividing node in the route, numbering the road segments (I + k)thI is a route number, k is a road section serial number, th is a road section number mark, and k belongs to [0, n ]]I.e. the route is divided into n +1 road segments;
s12, for any road section (I + k)thVirtual following vehicles VF and virtual leading vehicles VL are respectively arranged at the upstream detector node position Su and the downstream detector node position Sd; the real-time running speed of VL is calculated according to a speed detection value output by a downstream detector node position Sd detector, and the formula is as follows:
Figure FDA0002979155900000021
where T ∈ [ T ]i,Ti+1],TiA data timestamp for the downstream detector node location Sd detector,
Figure FDA0002979155900000022
respectively at time stamp T for the detectori、Ti+1The detected average traveling speed;
s13, according to the definition of the GM car following model on the operation parameter relation between the leading car and the car following, constructing a road section travel time estimation model GMTTE:
Figure FDA0002979155900000023
the model outputs a virtual following vehicle VF on a road section IthUpper travel time TTIAnd on the road section IthDownstream endpoint real time velocity
Figure FDA0002979155900000024
Wherein v isSd、vSuAs input values for the model, respectively for the section IthThe speed detection values output by the upstream detector and the downstream detector; l is a vehicleHead spacing index, m velocity index, α sensitivity; the process is repeated until the road segment (I + n) is completedthAnd estimating the route travel time.
3. The method for optimizing highway travel time estimation model parameters according to claim 2, wherein: in step S13, the route travel time is estimated, specifically,
s131, following vehicle VF on road section IthReal-time running speed at any time t of up running
Figure FDA0002979155900000025
The calculation formula is as follows:
Figure FDA0002979155900000026
in the formula
Figure FDA0002979155900000027
The running speed and the acceleration of VF at the time of T-delta T and the real-time acceleration
Figure FDA0002979155900000028
The specific calculation formula is as follows:
Figure FDA0002979155900000029
wherein a (—) is the sensitivity,
Figure FDA00029791559000000210
the running speed of the lead vehicle at the moment T-delta T,
Figure FDA00029791559000000211
respectively the running distance of the leading vehicle and the following vehicle at the time of T-delta T and the real-time running distance of the VL of the leading vehicle
Figure FDA00029791559000000212
The calculation formula is as follows:
Figure FDA00029791559000000213
real-time driving distance of following vehicle VF
Figure FDA00029791559000000214
The calculation formula is as follows:
Figure FDA00029791559000000215
in the formula
Figure FDA00029791559000000216
The running speed of the lead vehicle at the moment T-delta T,
Figure FDA00029791559000000217
for the running distance of the following vehicle at the time T-delta T,
Figure FDA00029791559000000218
the acceleration of VF at the time T-delta T;
s132, taking the road section IthEnd point real time velocity vTTIFor following car VF on the next road section (I +1)thInitializing the speed of the starting point;
s133, estimating model by using road section travel time
Figure FDA0002979155900000031
Estimation section (I +1)thThe travel time of (a);
s134, circulating the steps S132 and S133 until the road section (I + n) is finishedthA travel time estimate of (d);
s135, route travel time
Figure FDA0002979155900000032
Wherein TTIFor following vehicle VF on road section IthUpper travel time.
4. The highway travel time estimation model parameter optimization method of any one of claims 1-3, wherein: in step S3, specifically, the step,
s31, initializing weights, i.e., p (j) ═ Wj; the prior distribution p (j) is selected according to the traffic flow running state, and the traffic flow running state comprises a free flow state and a congestion state;
s32, calculating an error index MAj(l, m, α), adding MAjThe minimum value of the corresponding j is taken as the optimal time interval; the genetic algorithm outputs an optimal solution every iteration
Figure FDA0002979155900000033
Wherein M is the number of iterations;
s33, passing the optimal solution
Figure FDA0002979155900000034
And updating the prior distribution in the two operation states in the step S31 to generate the posterior distribution of the optimal solution.
5. The method of optimizing highway travel time estimation model parameters according to claim 4, wherein: in step S31, the prior distribution p (j) is selected according to the traffic flow running state, specifically,
using uniform probability distribution in free-flow regime, i.e.
Figure FDA0002979155900000035
σ1、σ2The upper and lower limits of j are defined according to the definition of the value range in S2, σ1=2,σ2=K;
Using lognormal distribution in congested conditions, i.e.
Figure FDA0002979155900000036
μ and σ are the mean and standard deviation of j, respectively.
6. The method of optimizing highway travel time estimation model parameters according to claim 4, wherein: in step S33, specifically, the step,
s331, use highThe gaussian distribution represents the known optimal solution joldAnd iterating the newly generated optimal solution jnewThe probability relationship between p (j)new|jold)=N(joldr) Wherein j isoldThe initial value is set to a non-negative number, σrIs the step length;
s332, calculating likelihood ratio r, and judging jnewWhether it is acceptable; in the free flow state, the calculation formula of r is as follows:
Figure FDA0002979155900000041
in the congestion state, the calculation formula of r is as follows:
Figure FDA0002979155900000042
if r > 1, then jnewAcceptable, the current optimal solution is calculated by joldIs updated to jnewOtherwise, it remains as jold
S333, performing N-fold loop on the steps S331 and S332 to obtain the optimal solution J of the time interval J and the corresponding weight WJ
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